Most people off the street would agree that a suit is more dignified, and it's not without reason. Wearing a suit indicates a level of discipline, effort, and intention about the way that you look that simply wearing a t shirt with jeans does not.

To contrast, the historical reason for the t shirt / jeans combo is practicality and convenience; tech as an industry got away with it at first, because techies were not interfacing with clients directly or simply because they're working class.

You can argue about the elitism and class differences surrounding suits versus t shirts and jeans, but I think it's a bit ridiculous to say that suits aren't aesthetically better just because of the media image for hacker types.